(1) Field of the Invention
The present invention pertains to a bottle neck alignment mechanism for an air conveyor system of the type that conveys plastic bottles and in particular to an alignment mechanism that precisely horizontally and vertically positions necks of the bottles conveyed into the air conveyor.
(2) Description of Related Art
Air conveyors are used for rapidly transporting plastic bottles or other light weight articles between work stations as, for example, from a blow molding station to a storage station or palletizing station. An example of this type of air conveyor is disclosed in U.S. patent application Ser. No. 08/792,659 filed Jan. 31, 1997 and patented May 16, 2000 as U.S. Pat. No. 6,026,773. This co-assigned application is incorporated herein by reference. A typical air conveyor includes a pair of laterally spaced, parallel flanges that define an elongate, longitudinal slot and a series of air jets on opposite sides of the slot. The plastic bottles are formed with annular rings around their necks. With the bottle necks extending through the slot and the rings overlying the spaced flanges, the bottles are suspended from the flanges and hang below the slot. Pressurized air supplied through an air plenum to the air jets is ejected from the jets and directed in streams toward the bottles. The bottles are pushed through the slot by the force of the air streams directed against the bottles.
Generally, to feed a stream of plastic bottles into the slot of an air conveyor, the bottles are typically placed in their upright orientations on a top surface of an endless belt conveyor. The belt conveyor conveys the bottles to an inlet end of the air conveyor slot. The belt conveyor is positioned so that the necks and rings of the bottles conveyed by the conveyor will align with the inlet end of the conveyor slot with the neck rings being received on the flanges of the conveyor slot. To assist in alignment of the bottle necks and rings with the air conveyor slot as they are transported by the belt conveyor toward the input of the air conveyor slot, the air conveyor is typically provided with a pair of laterally spaced guide plates that project horizontally from the opposite sides of the air conveyor slot toward the belt conveyor and the approaching stream of plastic bottles. The guide plates have mutually opposed edges that are aligned with the opposed edges of the air conveyor flanges at the inlet to the air conveyor slot. The mutually opposed edges of the guide plates diverge away from each other as the guide plates extend from the air conveyor inlet toward the approaching stream of bottles on the belt conveyor. As the bottles are conveyed by the belt conveyor toward the air conveyor slot, their necks pass between the guide plate edges with their annular neck rings positioned just above the horizontal positions of the guide plates. As the bottles are moved closer to the air conveyor slot, the opposed guide plate edges merge toward each other and toward the flanges of the air conveyor slot and work together in aligning the necks of the approaching stream of bottles horizontally, thus aligning the bottle necks with the air conveyor slot. An example of the guide plates that align the bottle necks horizontally relative to the air conveyor slot is disclosed in the co-assigned U.S. Pat. No. 6,026,773, referenced earlier.
The plastic bottles of the type conveyed by the air conveyor described above are the conventional type of plastic bottles used as containers for carbonated beverages and other types of beverages. The plastic bottle has a neck at its top that surrounds an opening of the bottle. The neck typically has exterior screw threading for receiving a cap. As the bottle extends downwardly from the neck, it tapers outwardly to an annular shoulder of the bottle defining the upper portion of the main receptacle or body of the bottle. An outwardly projecting annular rim or ring surrounds the bottle neck separating the neck from the annular shoulder. Plastic bottles of this type are provided in a variety of sizes and configurations.
Plastic bottles of this type are typically manufactured by blow molding. The plastic bottle is blow molded from a plastic parison. When removed from the mold, the plastic blow molded bottle is allowed to cool and at times the cooling of the bottle will result in slight variations in dimensions from one blow molded bottle to the next. This characteristic of blow molded bottles has created problems in the conveying of plastic bottles described earlier, and in particular transferring plastic bottles from a belt conveyor to an air conveyor.
In some designs of plastic bottles, the portion of a plastic bottle between its neck ring and the annular shoulder of the bottle has a very small vertical dimension. In transferring a plastic bottle from a belt conveyor to an air conveyor employing the guide plates described earlier, the plastic bottle must be transferred onto the guide plates so that the annular neck ring of the bottle is received in sliding engagement on top of the guide plates and the guide plates are received in the limited vertical space between the neck ring and bottle shoulder. In the blow molding of bottles, the vertical dimension between the top most edge of the bottle neck and the annular neck ring can be controlled accurately. However, the vertical distance between the bottom surface of the blow molded bottle and the annular neck ring can vary from one bottle to the next, for example by as much as plus or minus 1/18 of an inch. With such a variation in the vertical positioning of a plastic bottle annular neck ring above the bottom surface of the bottle and the surface of the belt conveyor conveying the bottle to an air conveyor, at times the annular neck ring of a plastic bottle will not align vertically relative to the guide plates of an air conveyor. This often results in the bottle being knocked over on the belt conveyor as it is conveyed toward the air conveyor which can result in disrupting the stream of bottles being conveyed to the air conveyor by the belt conveyor.
What is need to overcome the disadvantages associated with transferring plastic bottles from a belt conveyor to an air conveyor is a way of positively locating the annular neck ring of each plastic bottle in a stream of plastic bottles relative to the flanges of the air conveyor so that the receipt of the annular neck ring of the bottle on the pair of flanges of the air conveyor is assured.